(Not Applicable)
(Not Applicable)
The present invention generally relates to transformers and more particularly to a transformer which prevents lead breakage of the wire coil.
Typically, a transformer is formed by wrapping layers of wire around a cylindrical bobbin. In this respect, a first layer of wire is wrapped around the bobbin and at least one other layer is wrapped thereover. By varying the turns between the layers, it is possible to vary the voltage across each winding.
On encapsulated transformers, the leads of the wire layers are prone to breakage where they exit the encapsulation material. Specifically, the encapsulation material is typically a resin which is poured over the layers of wire. The ends of the wire must exit this encapsulation material in order to be attached to a power source and/or load. The typical approach for preventing breakage of the wire leads is to solder a insulated, stranded wire to the wire layer wrapped around the bobbin. The solder connection with the insulated stranded wire is covered with the encapsulation material and provides flexibility and strain relief for the wire layer wrapped around the bobbin of the transformer.
However, a problem exists in the fact that the solder connections and additional insulation tape of the stranded wire increases the coil diameter of the transformer. Accordingly, when many secondary windings are used on the transformer (i.e., in high voltage transformer design), reliability is decreased while manufacturing costs are increased. Additionally, the insulated stranded wire must be soldered by hand such that automated manufacturing processes may not be used to make the transformer.
The present invention addresses the above-mentioned deficiencies in the prior art transformer design by providing a new bobbin design which increases reliability and improved production yields with lower manufacturing costs. In this respect, the transformer with the novel bobbin design of the present invention allows for automated wire bonding to the finished transformer assembly thereby reducing manufacturing costs and increasing yields.
An improved high voltage transformer comprising a generally cylindrical bobbin. A plurality of windings, each with a respective first and second end, are wrapped around the bobbin. Attached in generally perpendicular relation to the bobbin is a bobbin end plate. Disposed on the bobbin end plate are a plurality of a first end lead breakouts and a plurality of second end lead breakouts. In this respect, respective ones of the first ends of the wire are attached to respective ones of the first end lead breakouts while respective ones of the second end of the wires are attached to respective ones of the second end lead breakouts in order to prevent breakage of the windings.
In accordance with the preferred embodiment of the present invention, the bobbin end plate is a printed wiring board such that the first and second end lead breakouts are formed from etched copper traces. The transformer further includes a core disposed about the windings. Additionally, an encapsulation layer is disposed over the windings and insulation is disposed between each layer of winding.
In order to facilitate attachment of a power supply and/or a load to the transformer, the transformer further comprises a plurality of winding termination pads disposed on the bobbin end plate. Additionally, the transformer will include a plurality of winding termination traces disposed on the bobbin end plate which are in electrical communication with respective ones of the winding termination pads. Each of the winding termination traces is in electrical communication with a respective one of the first end lead breakouts or a respective one of the second end lead breakouts. Each of the winding termination pads are disposed on a peripheral edge of the bobbin in order to facilitate attachment of a load or power supply thereto.
In accordance with the present invention there is a method of forming an improved high voltage transformer. The method comprises winding a first layer of wire around a bobbin having an end plate. Next, a first end of the wire is attached to a first end lead breakout of the end plate and a second end of the wire is attached to a second end lead breakout of the end plate. By attaching the first and second ends to respective first and second lead breakouts, breakage of the wire is prevented. It will be recognized that subsequent layers of wires may be wrapped around the bobbin and respective first and second ends thereof are attached to respective first and second lead breakouts of the bobbin endplate. In order to finish the transformer, the layers of wire may be encapsulated by a material and a core may be disposed thereover.